The present invention relates to the field of metal plating of articles, and in particular to masking articles, including those having a recess or bore therein.
In the manufacturing industry, it is often considered desirable to metal plate articles, that is to cover articles with a thin layer of metal, so that the article becomes stronger, more durable and corrosion resistant. This method of metal plating may be achieved by electro-plating for example, where an article is immersed in a metallic solution and subjected to an electric current. Such a metal plating technique generally results in the whole of the article being plated in metal, which may be undesirable, for example, where the article has a bore or a recess. Often it is desirable to coat just the outer areas of the article whilst leaving the recess or bore untreated. This is usually achieved by masking the recess or bore such that the metal is prevented from adhering to that part of the article.
A known method of masking recesses or bores is to coat the recess or bore with a non-conductive lacquer to which the metal is unable to adhere. The lacquer is generally applied to the recess or bore manually using a brush. Before the metal plating process is undertaken, the lacquer is allowed to dry and any excess lacquer is removed.
This method of masking, however, is time consuming, very labour intensive, and messy. Additionally, following the metal plating process, the lacquer must then be removed from the article by immersion in a degreaser, which uses trichloroethlene and which has health and safety implications and environmental implications due to solvent emissions.
The present invention seeks to overcome the disadvantages of the present masking method, and seeks to provide a quicker, cleaner and less labour intensive method of metal plating an article including those having a recess or bore therein.
According to the present invention there is provided a frame having a plurality of sealing members positioned thereon, the frame being capable of conducting an electrical current between sealing members, each sealing member being adapted to be in close contact with part of an article to be located thereon and to thereby substantially prevent fluid from touching that part of the article or entering into a bore or recess of the article, each sealing member further being adapted to conduct current between the frame and the article.
A force exerting device is advantageously provided on the frame for exerting the force on the article to hold the article firmly in close contact with a sealing member.
The force exerting device preferably comprises a resiliently biased member.
The sealing members may be substantially planar. Alternatively sealing members may be adapted to extend at least part way into a recess or bore of the article to be located thereon.
The frame exerting device may be adapted to hold the article between two sealing members. Alternatively the force exerting device may be adapted to hold the article between the force exerting device and a sealing member.
The sealing members may be substantially spherical or hemi-spherical. Alternatively the sealing members may be frusto-conical. The sealing members may be formed from titanium.
Alternatively the sealing members may comprise an electrically conductive core substantially encased in an electrical insulator material such as steel encased in plastic, for example. Alternatively the sealing members may be formed from a compressible, non-conductive material.
An electrically conductive member, such as a wire or spring for example, may extend from the frame through a sealing member such that the electrically conductive member is capable of forming an electrical contact between an article located on the sealing member, and the frame. The frame is preferably coated in a non-conductive material to prevent the frame from becoming metal plated when a current is applied to the frame and it is exposed to a metallic solution.
According to the present invention there is further provided a frame having a plurality of sealing members positioned thereon, the frame being capable of conducting an electrical current between sealing members, each sealing member being adapted to extend at least part way into a recess or bore of an article to be located thereon and to substantially prevent fluid from entering into the bore or recess of the article, each sealing member further being adapted to conduct current between the frame and the article.
According to the present invention in another aspect thereof, there is provided a method of metal plating an article having a bore provided therein, wherein the article is masked for plating by positioning a sealing member such that it extends through the bore and acts to seal the bore, substantially preventing plating fluid from entering therein, the sealing member being a length of foam which is compressed and passed through the bore of the article to seal the bore, a conductive wire being passed through the bore with the foam and being positioned so as to be in contact with the article, to enable a current to flow through the article during electro-plating.
The foam is preferably impermeable, and advantageously expands on heating. The foam may be expanded polyethylene cord. Preferably the foam has a diameter larger than that of the bore before compression. The foam is preferably heated before the electroplating process such that the foam expands and provides an effective seal to prevent liquid from entering the bore.
According to the present invention in another aspect thereof there is provided a method of metal plating an article wherein the article is masked for plating by positioning a sealing member such that it is in close contact with a part of the article and acts to seal off that part of the article, substantially preventing plating fluid from touching that sealed off part of the article, and wherein the article is firmly held in position against the sealing member by a force exerting device.
The sealing member may be located on a frame. Preferably the force exerting device is provided on the frame for allowing an article to be held firmly adjacent the sealing member. When the article is firmly held in the frame, at least part of the frame, and the article are exposed to a metallic solution. The frame is advantageously capable of conducting current, such that the current flows through the article held in the frame. The article is preferably dipped, whilst held in the frame, in a metallic solution. As the article is dipped in the metallic solution a current flows through the article and causes the article to become metal plated. Cadmium may be present in the solution so that the article becomes plated in cadmium.